This invention relates generally to a method for removing iodide compounds from non-aqueous, organic media, such as acetic acid.
The present invention is concerned with the problem of removing iodide compounds which are present, typically in small quantities, in certain non-aqueous organic media. Of particular concern is the presence of small amounts of iodide compounds such as methyl iodide, sodium iodide, and hydrogen iodide, in acetic acid. Such iodide contamination can be of great concern to the users of the acetic acid as it may cause processing difficulties when the acetic acid is subjected to subsequent chemical conversion. The iodide compounds present in the acetic acid may also cause iodide contamination of any other material to which is added.
A need therefore exists for an economically reasonable, commercially acceptable method for the removal of iodide compounds from non-aqueous, organic media, such as acetic acid.
Heretofore certain approaches to the removal of iodide compounds from various aqueous and non-aqueous media have been undertaken. To the extent that the approaches discussed below have related to the removal of iodide compounds from non-aqueous, organic media, they have not found commercial acceptability for large scale industrial processes.
The use of ion-exchange resins to remove iodine and/or iodide compounds from certain liquid or gaseous streams has been taught with respect to certain specific ion-exchange resins. Thus, the use of a H-type strongly acidic cation-exchange resin, such as an RSO.sub.3 H-type, in a column (in combination with an anion-exchange resin with quaternary ammonium groups and a free-base type anion-exchange resin with ternary amine groups) to remove iodine and alkyl iodide from aqueous solutions or gases, is taught in Japanese Pat. No. 73 37,762 published Nov. 13, 1973.
U.S. Pat. No. 3,943,229 shows the use of certain cross-linked acrylic anion exchange resins to remove iodine and compounds thereof from gaseous streams. In U.S. Pat. No. 4,238,294, various ion-exchange resins are employed to remove heavy metal ions and in some instances halogen values, from certain carboxylic acid solutions, principally through the use of strongly basic anion exchange resins.
Likewise, macroporous styrene-divinylbenzene copolymers have been shown to be effective in absorbing methyl iodide from air, as taught in F. Cejnav,Jad. Energ., 18(6), 199 (1972).
The use of silver-impregnated supports has also been taught. A gel-type ion exchange resin impregnated with silver by soaking in a silver-nitrate solution has been indicated to be useful in absorbing iodine and methyl iodide from an aqueous medium, as discussed in Hingorani et al, Chem Eng. World, 12(5) 59-60, 1977. Molecular sieves loaded with silver ions have also been indicated to be useful for the removal of methyl iodide from gaseous streams, as taught in Donner et al, Kerntechnik, 14(1), 22-8 (1972) and U.S. Pat. No. 3,658,467. Likewise, a column of silica impregnated with silver nitrate has been stated to be effective in removing methyl iodide in the vapor phase, as shown in U.S. Pat. No. 3,838,554.
In U.S. Pat. No. 4,088,737 mention is made of the use of silver-exchanged zeolite to remove iodine from a waste gas stream and the subsequent regeneration of the zeolite by use of hydrogen to remove the iodine which is in turn absorbed onto a lead-exchanged zeolite.
Another means for removing methyl iodide in a vapor phase process is discussed in West German Pat. No. 2,645,552 wherein a ceramic material having a surface area of 5-250 M.sup.2 /g impregnated with mixtures of water and triethylenediamine is employed.
The use of carbonaceous materials to remove iodine or iodide compounds from aqueous solution has been known for a long period of time, and is discussed, for example, in U.S. Pat. No. 1,843,354. The removal of methyl iodide using charcoal with triethylenediamine is discussed in Bonhate et al, Proc. Clean Air Conv., 114-119, 1972 and the use of activated charcoal impregnated with KSCN or SnI.sub.2 is shown in J. Nucl. Sci. Technol., 9(4), 197, (1972).
In a technical bulletin by Rohm and Haas dated September, 1978, Amberlyst.RTM.15, a strongly acidic resin having a macroreticular porous structure, is shown to be used to remove ferric ion from glacial acetic acid. In the same bulletin, it is also stated that Amerlyst.RTM.15 resin may be converted to any form such as sodium, potassium, and calcium by standard techniques employed in ordinary ion exchange processes.